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Inverse integral transformation method to derive local viscosity distribution measured by optical tweezers.
Soft Matter ( IF 2.9 ) Pub Date : 2020-07-01 , DOI: 10.1039/d0sm00887g
Ruri Hidema 1 , Zenji Yatabe , Hikari Takahashi , Ryusei Higashikawa , Hiroshi Suzuki
Affiliation  

Complex fluids have a non-uniform local inner structure; this is enhanced under deformation, inducing a characteristic flow, such as an abrupt increase in extensional viscosity and drag reduction. However, it is challenging to derive and quantify the non-uniform local structure of a low-concentration solution. In this study, we attempted to characterize the non-uniformity of dilute and semi-dilute polymer and worm-like micellar solutions using the local viscosity at the micro scale. The power spectrum density (PSD) of the particle displacement, measured using optical tweezers, was analyzed to calculate the local viscosity, and two methods were compared. One is based on the PSD roll-off method, which yields a single representative viscosity of the solution. The other is based on our proposed method, called the inverse integral transformation method (IITM), for deriving the local viscosity distribution. The distribution obtained through the IITM reflects the non-uniformity of the solutions at the micro scale, i.e., the distribution widens above the entanglement concentrations of the polymer or viscoelastic worm-like micellar solutions.

中文翻译:

逆积分变换法可得出用光镊测量的局部粘度分布。

复杂流体具有不均匀的局部内部结构。这在变形下会增强,从而引起特征性流动,例如拉伸粘度的突然增加和减阻。但是,对低浓度溶液的不均匀局部结构进行推导和量化具有挑战性。在这项研究中,我们尝试使用微观尺度上的局部粘度来表征稀,半稀聚合物和蠕虫状胶束溶液的不均匀性。分析了使用光镊测量的粒子位移的功率谱密度(PSD),以计算局部粘度,并比较了两种方法。一种是基于PSD滚降法,该方法可得出溶液的单一代表性粘度。另一个基于我们提出的方法,称为逆积分变换法(IITM),用于得出局部粘度分布。通过IITM获得的分布反映了溶液在微观尺度上的不均匀性,,分布在聚合物或粘弹性蠕虫状胶束溶液的缠结浓度之上加宽。
更新日期:2020-07-29
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